% d^2y/dt^2 - 7*(1-y^2)*dy/dt + y =0
% y(0) = 1 y'(0)=0
%   test
%   y(1) = y
%   y(2) = y'
%
%   dx(1)/dt = x(2)
%   dx(2)/dt = 1 - x(2)

function dy = example2(x,y)
    global a
    varphi = sqrt(3)/pi*log(a/(1-a));
    dy(1) = y(2);
    dy(2) = y(2)+ abs(y(2))*varphi;
end